It is well known to utilize drilling fluids, or drilling muds, in the drilling of oil, gas, and water wells. Typically, the drilling fluid is recirculated down through a hollow drill pipe, across the face of the drill bit and upward through the borehole. The drilling fluid serves multiple functions including transporting borehole cuttings to the surface, preventing the entry of formation fluids into the borehole, sealing the walls of the hole, cooling and lubricating the drill bit and stem, and providing a medium for hydraulic power for bottomhole cleaning. As the drilling mud is recirculated a deposit of the fluid, the drilling fluid filter cake, is deposited along the borehole walls.
After the borehole has been drilled, a casing is run into the well and cemented into place by pumping cement into the casing, displacing the cement into the annulus between the casing and borehole wall with drilling fluid or water, and allowing the cement to harden. The effectiveness of the seal formed by the cement between the casing and borehole surfaces is dependent upon the bonding of the cement to the casing and borehole surfaces.
There are a number of inherent disadvantages in the conventional method of cementing the casing in the borehole. First, the drilling fluid utilized during drilling must be removed from the borehole prior to introducing cement into the casing. Further, the effectiveness of the seal between the casing and the borehole surfaces can be adversely affected by the drilling fluid filter cake. Therefore, a need exists for a more efficient means for cementing the casing within the borehole and a more effective means for sealing the casing with the borehole surfaces.